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PT08 Metals and Metalloids
(PT141) Remediation of High pH and Hexavalent Chromium Ground Water with Carbonic Acid and Zero Valence Iron.
Hinckley, D.1, Rival, S.1, McLeod, C.2, 1 EA Engineering, Science, and Technology, Inc., Sparks, Maryland, United States2 EA Engineering, Science, and Technology, Inc., Newburgh, New York, United States
ABSTRACT- A full-scale carbon dioxide (CO2) and zero valence iron (ZFI) treatment system was developed to neutralize pH 13+ ground water and reduce hexavalent chromium (Cr+6) concentrations from approximately 0.5 mg/L to less than 0.01 mg/L, and total chromium to less than 0.1 mg/L. Ex situ CO2 aeration and ZFI was selected as the final remedial technology based on bench-scale study test results. This innovative combination was developed to address ground water that currently discharges into a wetland area. The desire was to treat the impacted water without construction of a costly treatment system that could require full-time operations. To assess the site-specific effectiveness of ex situ CO2 aeration, and to provide necessary data for design of the full-scale ex situ system, bench-scale testing was completed using ground water collected from the remedial target area. The bench-scale tests evaluated Cr+6 and pH against applied doses of CO2 and zero valence iron. The full-scale ex situ treatment system has been designed, based on the bench-scale testing results. To evaluate the effectiveness of the full-scale ex situ treatment system, pre- and post- samples will be collected and analyzed. The system is scheduled to be installed in 2003 with operational data collected monthly for the first 3 months. This presentation will detail the results of the bench-scale testing results for both unit processes, the design elements for the full-scale ex situ treatment system, and the results of the 3-month start-up and testing period of the full-scale system should they be available.
Key words: hexavalent chromium, ex situ remediation, bench-scale testing, zero valence iron
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